Hydraulic circuit for halting reciprocable rams



March 2, I948. L. c. COLE 2,437,077

HYDRAULIC CIRCUIT FOR HALTING RECIEPRQCABLUS RAMS Filed Jan. 18 19467Iuvzuron LYNDON C-COLE,

Patented Mar.2,

HYDRAULIC CIRCUIT FOR HALTING ICECIPROCABLE RAMS.

Lyndon 0. Cole, Cleveland, Ohio, asslgnor to H-P-M DevelopmentCorporation, Wilmington, Del., a corporation of Delaware ApplicationJanuary 18, 1946, Serial No. 641,991 I 6 Claims. 1

This invention relates to hydraulic apparatus and in particular toreciprocating hydraulic motors and control circuits therefor. L

In the usual reciprocating hydraulic motor,

there is an advancing means and a retracting means by which the ram ofthe motor is reciprocated. In reciprocating the motor, fluid is suppliedto one of the means while the other is exhausted. To halt thereciprocation of the ram it is customary to interrupt the fluid supplyto the one side or to bypass the fluid source to exhaust. This isordinarily accomplished by electrically operated valves which areactuated in response to a predetermined ram position or in response to apredetermined pressure condition created when the ram halts against aflxed abutment.

It has been found, however, that electrically actuated valves aresubject to sticking and the electric circuits for actuating the valvesare a source of trouble because of contacts burning, wires breaking,etc.

The particular object of the present invention is to provide a systemfor a reciprocating ram which includes improved means for halting theram by entrapping fluid in one end of the motor.

Another object is to provide means for halting a reciprocating hydraulicram at one end of its stroke without the use of electrically actuatedvalves.

Still another object is to provide an operating system for areciprocating hydraulic ram which operates to entrap fluid in one end ofthe motor cylinder to halt the ram by means of a valve which is operatedby the ram.

It is still another object to provide a hydraulic operating circuit fora reciprocating ram in which the movement of the'ram determines thepoint at which it will halt and in which the fluid source is bypassedwhen the ram comes to a halt,

These and other objects and advantages become more apparent uponreference to the following specification taken together with theaccompanying drawings in which:

Figure 1 is a diagrammatic view of a reciproeating hydraulic ram havingan operating and control circuit according to this invention; and

Figure 2 is a diagram of an electrical circuit adaptedfor controllingthe valves in the circuit of Figure 1.

Referring to the drawings, there is shown a reciprocating ram i0 havinga piston l2 slidable in the cylinder i4 and having connected therewith aplaten I6. The ram is bored as at Hi to receive the hollow boosterplunger that is ad- 2 Justably carried in the closed end of the cylinderl4.

The ram is provided with the bores 22 which communicate the working areaof the booster with the advancing area of the piston 12 when the ram hasadvanced a predetermined distance.

For supplying actuating fluid to the cylinder l4 to actuate the ram l0,there is provided a pump 24 which is connected to draw fluid from areservoir 28 and to discharge it under pressure through a conduit 28 tothe inlet of a four-way valve 30, The valve 30 comprises a service port32 that is connected by the conduit 34 with the retracting side of thepiston l2, and a service port 36 that is connected by the conduit 38with the bore in the booster plunger 20. The valve 30 also includes anexhaust connection 40 which returns fluid to the reservoir 26.

Reciprocable in the valve 30 is a valve member 42 that is normall heldin its center position by the opposed springs 44. In this position thefluid supplied by the pump 24 is bypassed through the exhaust connection40 back to the reservoir.

When the solenoid F at the right end of the valve is energized, thevalve member 42 moves leftwardly to connect the conduits 28 and 38 whileconnecting the conduit 34 with exhaust. When the solenoid R at the leftend of the valve is energized, the valve member 42 shifts rightwardly tointerconnect the conduits 28 and 34 while connecting the conduit 38 withexhaust. h

During the time that the ram is moving in the advancing direction due tofluid supplied to the booster plunger 20. the left end of the cylinderI4 is supplied with fluid through a conduit 46 which includes a surgecheck valve 48 that opens from the reservoir 26 toward the cylinder i4.When the ram III has advanced to the point that the bore l8 communicateswith the bores 22, the

check valve 48 closes and pressure may then be developed across theentire advancing surface of the piston '12.

When it is desired to retract the ram l0, fluid is supplied to theconduit 34 by shifting the valve member 42 and the left end of thecylinder I4 is exhausted directly to the reservoir through a valve50-which is connected in parallel with the surge check 48. The valve 50includes a valve member 52 normally urged by the spring 54 to interruptthe passage 56 which bypasses the check valve 48. In order to move thevalve member 52 into position where it establishes the passage 56, thereis provided the operating chamber 58 arranged in opposition to thespring 54 and connected by a conduit 80 with the conduit ll. Then, whenthe ram l moves in the retracting direction and reaches the point wherethe booster ram closes off the bores 22', fluid is entrapped in the leftend of the cylinder l4 and pressure is developed in the conduit 34suilicient to lift the valve member 52 and thus to exhaust the said leftend of the cylinder to permit uninterrupted retracting movement of theram l0.

To bring the ram III to a positive halt at a predetermined point in itsretracting movement, there is provided a valve 62 in the conduit 60which includes a valve member 64 normally urged by a spring 88 tomaintain the continuity of the conduit Bll. The valve chamber 84 ismovable into a second position where the conduit 80 is interrupted andis connected instead with a con duit 68 that leads to the reservoir.with the valve member in this position, the chamber 58 is exhausted andthe spring 54 returns the valve member 50 to its passage interruptingposition so that fluid is entrapped in the left end of the cylinder M,and the ram ill comes to a positive stop against a body of cushioningfluid.

For actuating the valve member 6!, there is preferably provided a camIll that is carried on an arm 12 that is adiustably secured to theplaten It as by the set screw 14. 4

In order to bypass the pump 24 when the ram has been halted by theaforementioned entrapping of fluid, there is provideda normally closedpressure switch 82 which is connected with the conduit 34 to be openedin response to a predetermined pressure therein greater than thepressure normally required to retract the ram III.

In Figure 2 is illustrated the electrical diagram for actuating thesolenoids F and R and including the switch 82. In this view the powerlines are indicated at LI and L2 and connected therebetween in serieswith the solenoid F is a start switch 80 which, when closed, energizesthe solenoid F to shift the valve member 42 to commence the advancingmovement of the ram Id. The solenoid is maintained energized through theholding circuit which includes the blades Fl of the solenoid F and thenormallyclosed switch SI. The ram continues on its advancing or-workingmovement until the switch SI is opened by a predetermined stimulus suchas a pressure means, a positionally responsive means, other automaticmeans or by manual means.

Also connected between the lines Li and L2, and in series with thesolenoid R, is a second blade of the switch SI which, when the saidswitch is actuated, closes to energize the solenoid R to shift the valvemember 42 rightwardly to commence the retracting movement of the ramill. The solenoid R is maintained and energized by the blades Ri thereofuntil the switch S2 is opened by a predetermined pressure developed inthe conduit 34.

It will be seen that this invention provides means for halting areciprocating ram at any point in its movement and does so without theuse of unreliable electrical equipment including contacts, solenoids,etc., but employs instead a valve which is positively actuated intoposition to effect the said halting of the ram. Furthermore, the ramcomes to halt against a body of fluid which is somewhat elastic and,therefore, has advantages over a solid abutment. In addition, thisinvention provides means for unloading the pump after the ram has beenhalted so that there is a minimum of power loss during 4 the idle periodof the ram regardless of its halting position.

It will be understood that this invention is susceptible to modificationin order to adopt it to difierent usages and conditions and,accordingly, it is desired to comprehend such modifications within thisinvention as may fall within the scope of the appended claims.

I claim:

1. In a hydraulic system; a fluid motor having an inlet and an outlet; afluid source connected to said inlet; a normally closed bypass valveconnected with said outlet; said motor having a valve actuating means;fluid pressure responsive means associated with said valve connectedwith said inlet and responsive to fluid pressure in the latter foractuating said valve into openposition; other valve means, said othervalve means having a protruding part normally projecting into the pathof said valve actuating means to disconnect said pressure responsivemeans from said inlet and connect the same instead to exhaust; and aconduit from said other valve to said bypass valve whereby uponactuation of the protruding part of said other valve by said actuatingmeans, fluid pressure is blocked off and said bypass valve is closed andvented to said exhaust by way of said other valve.

2. In a hydraulic system; a fluid motor having an inlet and an outlet; apressure connection to said inlet and an exhaust connection to saidoutlet; a normally closed bypass valve means connected to said outlet;rneans responsive to a predetermined pressure of said inlet foractuating said valve means into an open position; said motor having avalve actuating means; other valve means having a part projecting intothe path of said valve actuating means responsive to a predeterminedmovement of said motor; valve actuating means for actuating said partfor disconnecting said other valve means from said inlet pressure, andconnecting the same to said exhaust.

3. In a hydraulic system; a fluid motor having an inlet and an outlet; afluid source connected to said inlet; a normally closed bypass valveconnected with said outlet; said motor having a cam; fluid pressureresponsive means associated with said valve connected with said inletand responsive to fluid pressure in the latter for actuating said valveinto open position; other valve means, said other valve means having aprotruding part normally projecting into the path of said cam todisconnect said pressure responsive means from saidinlet and connect thesame instead to exhaust; and a conduit from said other valve to nectedto said outlet; means responsive to a predetermined pressure of saidinlet for actuating said valve means into an open position, said motorhaving a cam; other valve means having a part projecting into the pathof said cam responsive to a predetermined movement of said motor; saidcam being constructed and adapted to actuate said part for disconnectingsaid bypass valve means from said inlet pressure, and connecting thesame to said exhaust.

5 5. In a hydraulic system; a fluid motor havin an inlet and an outlet;a fluid source connected to said inlet; a normally closed bypass valveconnected with said outlet; said motor having a valve actuating means;fluid pressure responsive means associated with said valve connectedwith said inlet and responsive to fluid pressure in the latter foractuating said valve into open position; other valve means, said othervalve means having a protruding part normally projecting into the pathof said valve actuating means to disconnect said pressure responsivemeans from said inlet and connect the same instead to exhaust; and aconduit from said other valve to said bypass valve whereby uponactuation of the protruding part of said other valve by said actuatingmeans, fluid pressure is blocked oil and said bypass valve is closed andvented to said exhaust by way of said other valve; and a spring forbiasing said other valve into its normally closed position.

6. In a hydraulic system; a fluid motor having an inlet and an outlet; apump connected to said inlet; a normally closed bypass valve connectedwith said outlet; said motor having a valve actuating means; fluidpressure responsive means associated with said valve connected with saidinlet and responsive to fluid pressure in the latter for actuating saidvalve into open position; other valve means, said other valve meanshaving a protruding part normally projecting into the path 476,590

of said valve actuating means to disconnect said pressure responsivemeans from said inlet and connect the same instead to exhaust; and aconduit from said other valve to said bypass valve LYNDON' c. com.

REFERENCES CITED The following references are of record in the flle ofthis patent:

UNITED STATES PATENTS Number Name Date 2,164,971 Vickers July 4, 19392,258,981 Ernst Oct. 14, 1941 2,277,640 Harrington Mar. 24, 19422,293,334 Ernst Aug. 18, 1942 FOREIGN PATENTS Number Country Date GreatBritain Dec. 13, 1937

